Stomach Flashcards Preview

Give 4 functions of the stomach.

Which cells of the stomach produce gastric acid (HCL) and intrinsic factor?

Parietal cells

3

What do the chief cells of the stomach produce?

Pepsinogen

4

What do enterochromaffin-like (ECL) cells release?

Histamine

5

Which cells release gastrin?

G cells

6

What do D cells release?

Somatostatin

7

What is the lower portion of the stomach called?

Antrum

8

What is the role of the antrum?

Mixing the stomach contents

9

Describe how parietal cells produce HCL.

1. Water breaks down into OH- and H+2. CO2 from respiration is converted into H2O3 via carbonic anhydrase 3. H2CO3 rapidly dissociates into HCO3- and H+4. H+ react with OH- ions from the breakdown of water to regenerate H2O5. H+ from the breakdown of H2O are pumped into the stomach lumen via the H+/K+ ATPase pump in the luminal membrane of the parietal cells. 1 K+ ion is pumped in to the parietal cell for every 1H+ ion pumped out into the stomach 6. HCO3- is secreted into the capillary for the exchange of Cl- ions 7. Cl- ions diffuse into the stomach and combine with H+ to form HCL.

10

What inhibits the release of HCL from parietal cells?

What protects the stomach from its own acid?

Mucus

12

What stimulates the parietal cells to release HCL?

1. ECL cells releasing histamine 2. Gastrin binds to receptors on parietal cells which also stimulates the release of HCL3. Parasympathetic stimulation from the vagus nerve: acetylcholine binds to muscaranic receptors on both ECL and parietal cells.

Both gastrin and histamine increase the number of H+/K+ ATPase pumps on the plasma membrane of parietal cells

What is an ulcer?

A breach in a mucosal surface.

17

Which infection is the biggest cause of peptic ulcers?

Helicobacter pylori infection.

18

How does helicobacter pylori cause peptic ulcers?

The bacteria lives in the gastric mucus. 1. It secretes urease, splitting urea into CO2 and ammonia2. Ammonia combines with H+ to form ammonium which is toxic and results in less mucous production 3. Proteases and cytotoxin A released from the bacteria attack the gastric epithelium, further reducing mucous production

19

What is the treatment for infection by helicobacter pylori?

Triple therapy: proton pump inhibitor - inhibits H+ ions being pumped into lumen, increasing gastric PH to make conditions inhospitable for the bacteria.Antibiotics are given as well.

1.5L. Does this by smooth muscle and fundus receptive relaxation.

What is released by enteric nerves to receptively relax the stomach?

Describe how peristalsis drives food down the stomach.

1. Each wave begins in the body of the stomach. These initial contractions are too weak to produce much mixing of luminal contents with acid and pepsin. 2. More powerful contractions occur in the antrum, which enables better mixing of luminal contents 3. Pyloric sphincter between antrum and duodenum closes as peristaltic waves reach it. This ensures little chyme enters the duodenum.

36

Which cells determine the frequency of peristaltic waves?

Interstitial cells of Cajal in the muscular propria. These are pacemaker cells.

37

The pacemaker cells (Cajal) undergo slow depolarisation-repolarisation cycles. How are the waves of depolarisation transmitted to adjacent smooth muscle cells?